The basic goal of the proposed research is to investigate the role of cell-cell adhesion in the commitment of human mesenchymal stem cells (MSCs) to a smooth muscle fate. MSC commitment requires input from soluble growth factors as well as mechanical cues derived from cell-cell or cell-matrix contact. Inappropriate differentiation of circulating MSCs may contribute to the pathological accumulation of smooth muscle cells in arteriosclerotic plaques, yet the physiological signals regulating myogenic commitment of MSCs remain poorly understood. We have found that commitment of MSCs to become smooth muscle cells depends on cell density and cell-cell contact, and have identified candidates in this signaling transduction pathway. Here we propose investigating whether cell density regulates smooth muscle commitment through N-cadherin and Rac1 pathways. Specifically, we plan to test the effects of inhibiting N-cadherin or Rac1 on density- dependent myogenesis, using several approaches including dominant negative constructs, function blocking antibodies, and small molecule inhibitors. This project will provide new insights into the molecular basis for MSC myogenesis and may suggest new strategies for prevention or treatment of vascular disease. [unreadable] [unreadable] [unreadable]